The present disclosure relates generally to the field of automated maintenance (including nondestructive inspection) of aircraft structural elements such as airfoil-shaped bodies, and more particularly to an automated end effector-carrying apparatus that is coupled to and travels along an airfoil-shaped body having a relatively short chord length while performing a maintenance function. As used herein, the term “maintenance” includes, but is not limited to, operations such as nondestructive inspection (NDI), drilling, scarfing, grinding (e.g., to remove bonded or bolted components), fastening, applique application, ply mapping, depainting, cleaning and painting. Any one of a multiplicity of end effectors for performing a respective one of the foregoing maintenance functions can be attached to the apparatus. There are a number of types of blade components on aircraft that will benefit from maintenance automation, including rotorcraft blades, propeller blades, flaps, ailerons, trim tabs, slats, stabilators and stabilizers. As a whole, the automated apparatus reduces maintenance time, labor hours and human errors when robotic maintenance functions are performed on blade components.
U.S. patent application Ser. No. 13/663,709 discloses automated apparatus for performing maintenance functions on airfoil-shaped bodies having short chord lengths, without the necessity of removing the airfoil-shaped body from the aircraft. One such apparatus comprises a platform, an end effector carried by the platform, the end effector being selected from a group of interchangeable end effectors, means for mounting the end effector-carrying platform on an airfoil-shaped body, means for moving the end effector-carrying platform in a spanwise direction along the airfoil-shaped body, and means for moving the end effector in a chordwise direction relative to the airfoil-shaped body when the platform is stationary. In one implementation, the automated apparatus comprises a blade crawler which is movable in a spanwise direction and comprises a traveling element (e.g., a slider) that is linearly translatable in a chordwise direction when the spanwise-movable blade crawler is stationary. The selected end effector (mounted to the aforementioned slider) can be moved in a chordwise direction when the blade crawler is stationary.
The above-described blade crawler was designed to use the leading and trailing edge features of the blade to maintain its alignment with the blade. In practice, however, it can be difficult to maintain crawler alignment on complexly curved blades with twist, camber and sweep. A prototype blade crawler was developed having unidirectional rubber alignment wheels which tended to track along only straight paths along the blade. Although this crawler tracked well when traversing a constant-profile section of a blade, it tended to fall off the leading edge of the blade when encountering a section having a non-constant profile or complex curvature. The unidirectional rubber alignment wheels would continue along a straight path, even when the leading edge of the blade formed a curved path.
Another problem afflicting the aforementioned blade crawler prototype was an inability to traverse over trailing edge protrusions such as trim tabs, trim tab covers, and other irregularities. This inability to traverse trailing edge protrusions was mainly caused by a small-diameter follower wheel that is unable to climb over protrusions larger than its own radius.
An enhanced blade crawler capable of maintaining crawler alignment along a curved leading edge and/or traversing over trailing edge protrusions of a blade component would be advantageous.